Wireless Networking Technologies

8/17/2019 Wireless Networking Technologies

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Wireless Networking TechnologiesWLAN, WiFi Mesh and WiMAX


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Sridhar Iyer IIT Bombay 2

Course Outline

Wireless Networks – Difference fro wired – Mo!ilit"

#F $asics – Fre%uenc", odulation – Mediu access control

WiFi O&er&iew – $asic ele ents – 'tandards and &ariants

WiMaX O&er&iew – $asic ele ents

Wireless LANs (WiFi) – *+ -.. standards – Mo!ilit" su//ort – 0oice and 1o' su//ort

Mesh and Adhoc Networks – #outing and Trans/ort

Wireless MANs (WiMaX) – *+ -.2 standard – 0oice and 1o' su//ort

Trends – O&erla" networks


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Wireless Networks


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Wireless networks Access co /uting3co unication ser&ices, on the o&e

Wireless WANs – Cellular Networks4 5'M, 56#', CDMA – 'atellite Networks4 7ridiu

Wireless LANs – WiFi Networks4 *+ -.. – 6ersonal Area Networks4 $luetooth

Wireless MANs – WiMaX Networks4 *+ -.2 – Mesh Networks4 Multi8ho/ WiFi – Adhoc Networks4 useful when infrastructure not a&aila!le


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Li itations of the o!ile en&iron ent

• Li itations of the Wireless Network• li ited co unication !andwidth• fre%uent disconnections• heterogeneit" of frag ented networks

• Li itations 7 /osed !" Mo!ilit"• route !reakages• lack of o!ilit" awareness !" s"ste 3a//lications

• Li itations of the Mo!ile De&ice• short !atter" lifeti e• li ited ca/acities


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Mo!ile co unication

Wireless &s- o!ile 9:a /les stationar" co /uter

la/to/ in a hotel (/orta!le) wireless LAN in historic !uildings 6ersonal Digital Assistant (6DA)

7ntegration of wireless into e:isting fi:ed networks4 – Local area networks4 7999 *+ -.., 9T'7 (;769#LAN) – Wide area networks4 Cellular


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Wireless &3s Wired networks

#egulations of fre%uencies – Li ited a&aila!ilit", coordination is re%uired – useful fre%uencies are al ost all occu/ied

$andwidth and dela"s – Low trans ission rates

= few >!its3s to so e M!it3s- – ;igher dela"s

= se&eral hundred illiseconds – ;igher loss rates

= susce/ti!le to interference, e-g-, engines, lightning Alwa"s shared ediu – Lower securit", si /ler acti&e attacking – radio interface accessi!le for e&er"one

– secure access echanis s i /ortant


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!/s

@2 >!/s

@? M!/s

M!/s

@8.. M!/s

.8 M!/s *+ -..

Wireless Technolog" Landsca/e

$luetooth

*+ -..!

*+ -..Ba,!Tur!o -..a

7ndoor

.+ –

Long rangeoutdoor

@> – +>

Long distanceco -

+ – @+>

µwave p-to-p links

-.. /8to8/ link

5


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#eference odel

A//lication

Trans/ort

Network

Data Link

6h"sical

Mediu

Data Link

6h"sical

A//lication

Trans/ort

Network

Data Link

6h"sical

Data Link

6h"sical

Network Network

#adio


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9ffect of o!ilit" on /rotocol stack

A//lication – new a//lications and ada/tations – ser&ice location, ulti ediaTrans/ort – congestion and flow control – %ualit" of ser&iceNetwork – addressing and routing – de&ice location, hand8o&er

Link – edia access and securit"6h"sical – trans ission errors and interference


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6ers/ecti&esNetwork designers 4 Concerned with cost8effecti&edesign – Need to ensure that network resources are efficientl" utiliEed

and fairl" allocated to different users -

Network users 4 Concerned with a//lication ser&ices – Need guarantees that each essage sent will !e deli&ered

without error within a certain a ount of ti e-

Network /ro&iders 4 Concerned with s"stead inistration – Need echanis s for securit", anage ent, fault8tolerance

and accounting-


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#F $asics


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Factors affecting wireless s"ste design

Fre%uenc" allocations – What range to o/erate Ma" need licenses-

Multi/le access echanis – ;ow do users share the ediu without interfering

Antennas and /ro/agation – What distances 6ossi!le channel errors introduced-

'ignals encoding

– ;ow to i /ro&e the data rate9rror correction – ;ow to ensure that !andwidth is not wasted


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Fre%uencies for co unication

0LF G 0er" Low Fre%uenc" H;F G Hltra ;igh Fre%uenc"LF G Low Fre%uenc" ';F G 'u/er ;igh Fre%uenc"MF G Mediu Fre%uenc" 9;F G 9:tra ;igh Fre%uenc";F G ;igh Fre%uenc" H0 G Hltra&iolet Light

0;F G 0er" ;igh Fre%uenc"

Fre%uenc" and wa&e length4 λ G c3fwa&e length λ , s/eed of light c ≅


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Wireless fre%uenc" allocation#adio fre%uencies range fro >;E to ?++5;I (7TH)

Microwa&e fre%uenc" range – . 5;E to ?+ 5;E – Directional !ea s /ossi!le – 'uita!le for /oint8to8/oint trans ission – Hsed for satellite co unications#adio fre%uenc" range –


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Fre%uencies for o!ile co unication

0;F83H;F8ranges for o!ile radio – si /le, s all antenna for cars – deter inistic /ro/agation characteristics, relia!le connections

';F and higher for directed radio links, satelliteco unication – s all antenna, focusing – large !andwidth a&aila!le

Wireless LANs use fre%uencies in H;F to ';F s/ectru – so e s"ste s /lanned u/ to 9;F

– li itations due to a!sor/tion !" water and o:"gen olecules(resonance fre%uencies)

= weather de/endent fading, signal loss caused !" hea&"rainfall etc-


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Fre%uenc" regulations

Fre%uencies fro >;E to


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Wireless trans ission

Wireless co unication s"ste s consist of4 – Trans itters – Antennas4 radiates electro agnetic energ" into air

– #ecei&ers7n so e cases, trans itters and recei&ers areon sa e de&ice, called transcei&ers-

Transmitter Receiver

ntennantenna


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Trans itters

m!"i#ier

$sci""ator

%i&er 'i"ter m!"i#ier ntenna

Transmitter

S(!!ose yo( )ant to *enerate a si*na" that is sent at 900 %+, andthe ori*ina" so(rce *enerates a si*na" at 300 %+,-

. m!"i#ier / stren*thens the initia" si*na"

.$sci""ator / creates a carrier )ave o# 600 %+,

.%i&er / combines si*na" )ith osci""ator and !rod(ces 900 %+,a"so does mod("ation etc

. 'i"ter / se"ects correct #re (ency

. m!"i#ier / Stren*thens the si*na" be#ore sendin* it

So(rce


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Antennas


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Antennas An antenna is an electrical conductor or s"ste ofconductors to send3recei&e #F signals – Trans ission 8 radiates electro agnetic energ" into s/ace – #ece/tion 8 collects electro agnetic energ" fro s/ace

7n two8wa" co unication, the sa e antenna can !eused for trans ission and rece/tion

$mnidirectiona" ntenna "o)er #re (ency

irectiona" ntennahi*her #re (ency


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#adiation and rece/tion of electro agnetic wa&es,

cou/ling of wires to s/ace for radio trans ission7sotro/ic radiator4 e%ual radiation in all directions(three di ensional) 8 onl" a theoretical referenceantenna

#eal antennas alwa"s ha&e directi&e effects(&erticall" and3or horiEontall")#adiation /attern4 easure ent of radiation aroundan antenna

Antennas4 isotro/ic radiator

E"

:

E

" : idealisotro/icradiator


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Antennas4 si /le di/oles#eal antennas are not isotro/ic radiators – di/oles with lengths λ3? on car roofs or λ3 (;ertEian di/ole)

sha/e of antenna /ro/ortional to wa&elength5ain4 a:i u /ower in the direction of the ain lo!eco /ared to the /ower of an isotro/ic radiator (with thesa e a&erage /ower)

side &iew (:"8/lane)

:

"

side &iew ("E8/lane)

E

"

to/ &iew (:E8/lane)

:

E

si /ledi/ole

λ3? λ3


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Antennas4 directed and sectoriEed

side &iew (:"8/lane)

:

"

side &iew ("E8/lane)

E

"

to/ &iew (:E8/lane)

:

E

to/ &iew, < sector

:

E

to/ &iew, 2 sector

:

E

Often used for icrowa&e connections or !ase stationsfor o!ile /hones (e-g-, radio co&erage of a &alle")

directedantenna

sectoriEedantenna


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Antenna odels

In Omni Mode:Nodes recei&e signals with gain G o

In Directional Mode:

Ca/a!le of !ea for ing in s/ecified directionDirectional 5ain G d (G d > G o )


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Directional co unication

#ecei&ed 6ower ∝ (Trans it /ower)J(T: 5ain) J (#: 5ain)

Directional gain is higher

Directional antennas useful for4 7ncrease Krange , kee/ing trans it /ower constant #educe trans it /ower, kee/ing range co /ara!le

with o ni ode


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Co /arison of o ni and directional

7ssues O ni Directional

'/atial #euse Low ;igh

Connecti&it" Low ;igh

7nterference O ni Directional

Cost Co /le:it" Low ;igh


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Antennas4 di&ersit"5rou/ing of or ore antennas – ulti8ele ent antenna arra"s

Antenna di&ersit" – switched di&ersit", selection di&ersit"

= recei&er chooses antenna with largest out/ut

– di&ersit" co !ining= co !ine out/ut /ower to /roduce gain= co/hasing needed to a&oid cancellation

λ3?λ3λ3?

ground /lane

λ3λ3

λ3


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'ignal 6ro/agation and Modulation


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'ignals/h"sical re/resentation of datafunction of ti e and locationsignal /ara eters4 /ara eters re/resenting the &alue ofdataclassification – continuous ti e3discrete ti e – continuous &alues3discrete &alues – analog signal G continuous ti e and continuous &alues – digital signal G discrete ti e and discrete &aluessignal /ara eters of /eriodic signals4/eriod T, fre%uenc" fG.3T, a /litude A, /hase shift ϕ – sine wa&e as s/ecial /eriodic signal for a carrier4

s(t) G At sin( π f t t ϕt)


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'ignal /ro/agation ranges

distance

sender

trans ission

detection

interference

Trans ission range – co unication /ossi!le – low error rate

Detection range – detection of the signal/ossi!le

– no co unication/ossi!le

7nterference range – signal a" not !edetected

– signal adds to the!ackground noise


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Attenuation4 6ro/agation #ange


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Attenuation

'trength of signal falls off with distance o&ertrans ission ediu

Attenuation factors for unguided edia4

– #ecei&ed signal ust ha&e sufficient strength so thatcircuitr" in the recei&er can inter/ret the signal – 'ignal ust aintain a le&el sufficientl" higher than

noise to !e recei&ed without error

– Attenuation is greater at higher fre%uencies, causingdistortion

A//roach4 a /lifiers that strengthen higherfre%uencies


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'ignal /ro/agation6ro/agation in free s/ace alwa"s like light (straight line)

#ecei&ing /ower /ro/ortional to .3d(d G distance !etween sender and recei&er)#ecei&ing /ower additionall" influenced !" – fading (fre%uenc" de/endent)

– shadowing – reflection at large o!stacles – refraction de/ending on the densit" of a ediu – scattering at s all o!stacles

– diffraction at edges

reflection scattering diffractionshadowing refraction


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'ignal can take an" different /aths !etween sender and recei&er due toreflection, scattering, diffraction

Ti e dis/ersion4 signal is dis/ersed o&er ti e interference with Kneigh!or s" !ols, 7nter '" !ol 7nterference (7'7)

The signal reaches a recei&er directl" and /hase shifted distorted signal de/ending on the /hases of the different /arts

Multi/ath /ro/agation

signal at sender signal at recei&er

LO' /ulsesulti/ath

/ulses


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9ffects of o!ilit"

Channel characteristics change o&er ti e and location – signal /aths change – different dela" &ariations of different signal /arts – different /hases of signal /arts

%uick changes in the /ower recei&ed(short ter fading)

Additional changes in

– distance to sender – o!stacles further awa" slow changes in the a&erage /owerrecei&ed (long ter fading)

short ter fading

long terfading

t

/ower


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6ro/agation odes

arth

arth

arth

a ro(nd ave ro!a*ation

b S y ave ro!a*ation

c :ine/o#/Si*ht ro!a*ation

Transmissionntenna

Receivin*ntenna

Si*na"

Si*na"

Ionos!here

Si*na"


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ModulationDigital odulation

– digital data is translated into an analog signal (!ase!and) – A'>, F'>, 6'> – differences in s/ectral efficienc", /ower efficienc", ro!ustness

Analog odulation – shifts center fre%uenc" of !ase!and signal u/ to the radio carrier

Moti&ation – s aller antennas (e-g-, λ3?) – Fre%uenc" Di&ision Multi/le:ing – ediu characteristics

$asic sche es – A /litude Modulation (AM) – Fre%uenc" Modulation (FM) – 6hase Modulation (6M)


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Modulation and de odulation

s"nchroniEationdecision

digitaldataanalog

de odulation

radiocarrier

analog!ase!andsignal

.+..+.++. radio receiver

digitalodulation

digitaldata analog

odulation

radiocarrier

analog!ase!andsignal

.+..+.++. radio transmitter


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Digital odulationModulation of digital signals known as 'hift >e"ing

A /litude 'hift >e"ing (A'>)4 – &er" si /le – low !andwidth re%uire ents – &er" susce/ti!le to interference

Fre%uenc" 'hift >e"ing (F'>)4 – needs larger !andwidth

6hase 'hift >e"ing (6'>)4 – ore co /le: – ro!ust against interference

Man" ad&anced &ariants

. + .

t

. + .

t

. + .

t


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Multi/le:ing Mechanis s


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Multi/le:ing in ? di ensions – s/ace (s i) – ti e (t) – fre%uenc" (f) – code (c)

5oal4 ulti/le useof a shared ediu

7 /ortant4 guard s/aces neededP

s

s <

s .

Multi/le:ing

f

t

c

k k< k? k@ k2k.

f

t

c

f

t

c

channels k i


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Fre%uenc" ulti/le:'e/aration of the whole s/ectru into s aller fre%uenc" !ands

A channel gets a certain !and of the s/ectru for the wholeti e Ad&antages4no d"na ic coordinationnecessar"

works also for analog signals

Disad&antages4waste of !andwidthif the traffic isdistri!uted une&enl"infle:i!leguard s/aces

k k< k? k@ k2k.

f

t

c


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f

t

c

k k< k? k@ k2k.

Ti e ulti/le: A channel gets the whole s/ectru for a certain

a ount of ti e

Ad&antages4onl" one carrier in the

ediu at an" ti ethrough/ut high e&enfor an" users

Disad&antages4/recises"nchroniEationnecessar"


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f

Ti e and fre%uenc" ulti/le:

Co !ination of !oth ethods A channel gets a certain fre%uenc" !and for a certain a ountof ti e

9:a /le4 5'M Ad&antages4 – !etter /rotection against

ta//ing – /rotection against fre%uenc"

selecti&e interference – higher data rates co /ared to

code ulti/le:!ut4 /recise coordinationre%uired

t

c

k k< k? k@ k2k.


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Code ulti/le:9ach channel has a uni%ue code

All channels use the sa es/ectru at the sa e ti e Ad&antages4

– !andwidth efficient – no coordination and s"nchroniEation

necessar" – good /rotection against interference

and ta//ingDisad&antages4 – lower user data rates – ore co /le: signal regeneration7 /le ented using s/reads/ectru technolog"

k k< k? k@ k2k.

f

t

c


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CDMA 9:a /le – D G rate of data signal

– $reak each !it into k chips= Chi/s are a user8s/ecific fi:ed /attern – Chi/ data rate of new channel G kD

7fk G2 and code is a se%uence of .s and 8.s – For a ; . < !it, A sends code as chi/ /attern

= Qc., c , c


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CDMA 9:a /le

Hser A code G Q., = ., = ., ., = ., .R – To send a . !it G Q., = ., = ., ., = ., .R – To send a + !it G Q = ., ., ., = ., ., = .R

Hser $ code G Q., ., = ., = ., ., .R – To send a . !it G Q., ., = ., = ., ., .R

#ecei&er recei&ing with A


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'/read s/ectru technolog"6ro!le of radio trans ission4 fre%uenc" de/endent fadingcan wi/e out narrow !and signals for duration of theinterference'olution4 s/read the narrow !and signal into a !road !andsignal using a s/ecial code 8 /rotection against narrow!and interference

'ide effects4 – coe:istence of se&eral signals without d"na ic coordination – ta/8/roof

Alternati&es4 Direct 'e%uence, Fre%uenc" ;o//ing

detection atrecei&er

interference s/readsignal

signal

s/readinterference

f f

/ower /ower


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'/read8s/ectru co unications

'ource4 7ntersil


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9ffects of s/reading and interferenced63df

f i)

d63df

f ii)

sender

d63df

f

iii)

d63df

f

i&)

recei&er f

&)

user signal!road!and interferencenarrow!and interference

d63df


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D''' /ro/erties

'ource4 7ntersil


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D''' (Direct 'e%uence)XO# of the signal with /seudo8rando nu !er

(chi//ing se%uence) – an" chi/s /er !it (e-g-, . *) result in higher !andwidth of thesignal

Ad&antages – reduces fre%uenc" selecti&e

fading – in cellular networks= !ase stations can use the

sa e fre%uenc" range= se&eral !ase stations can

detect and reco&er the signal= soft hando&er Disad&antages – /recise /ower control necessar"

user data

chi//ingse%uence

resultingsignal

+ .

+ . . + . + . +. + + . ..

XOR

+ . . + + . + .. + . + +.

=

t!

tc

t! 4 !it /eriodtc4 chi/ /eriod


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D''' Trans it3#ecei&e

Xuser data

chi//ingse%uence

odulator

radiocarrier

s/reads/ectrusignal

trans itsignal

transmitter

de odulator

recei&edsignal

radiocarrier

X

chi//ingse%uence

low/assfilteredsignal

receiver

integrator

/roducts

decisiondata

sa /ledsu s

correlator

Fre%uenc" ;o//ing '/read


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Fre%uenc ;o//ing /read'/ectru (F;'')

'ignal is !roadcast o&er see ingl" rando series of radiofre%uencies'ignal ho/s fro fre%uenc" to fre%uenc" at fi:ed inter&alsChannel se%uence dictated !" s/reading code#ecei&er, ho//ing !etween fre%uencies in s"nchroniEationwith trans itter, /icks u/ essage

Ad&antages – 9a&esdro//ers hear onl" unintelligi!le !li/s – Atte /ts to Sa signal on one fre%uenc" succeed onl" at knocking

out a few !its


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F;'' (Fre%uenc" ;o//ing)

Discrete changes of carrier fre%uenc" – se%uence of fre%uenc" changes deter ined &ia /seudo randonu !er se%uence

Two &ersions – Fast ;o//ing4 se&eral fre%uencies /er user !it

– 'low ;o//ing4 se&eral user !its /er fre%uenc" Ad&antages

– fre%uenc" selecti&e fading and interference li ited to short /eriod – si /le i /le entation – uses onl" s all /ortion of s/ectru at an" ti eDisad&antages – not as ro!ust as D''' – si /ler to detect

l d


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'low and Fast F;''

user data

slowho//ing(< !its3ho/)

fastho//ing

(< ho/s3!it)

+ .

t!

+ . . t

f

f .

f

f <

t

td

f

f .

f

f <

t

td

t! 4 !it /eriod t d4 dwell ti e

i 3 i&


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F;'' Trans it3#ecei&e

odulator user data

ho//ingse%uence

odulator

narrow!andsignal

s/readtrans itsignal

transmitter

recei&edsignal

receiver

de odulator data

fre%uenc"s"nthesiEer

ho//ingse%uence

de odulator

fre%uenc"s"nthesiEer

narrow!andsignal

OFDM (O h l F % " Di&i i )


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OFDM (Orthogonal Fre%uenc" Di&ision)6arallel data trans ission on se&eralorthogonal su!carriers with lower rate

Ma:i u of one su!carrier fre%uenc" a//ears e:actl" at a fre%uenc"where all other su!carriers e%ual Eero

su/er/osition of fre%uencies in the sa e fre%uenc" range

k<f

t

c

A /litude

f

su!carrier4'7 functionG sin(:):

OFDM


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OFDM6ro/erties – Lower data rate on each su!carrier less 7'7 – interference on one fre%uenc" results in interference of one

su!carrier onl" – no guard s/ace necessar" – orthogonalit" allows for signal se/aration &ia in&erse FFT on

recei&er side

– /recise s"nchroniEation necessar" (sender3recei&er)

Ad&antages – no e%ualiEer necessar" –

no e:/ensi&e filters with shar/ edges necessar" – !etter s/ectral efficienc" (co /ared to CDM) A//lication

– *+ -..a, ;i/erLAN , AD'L


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ALO;A

'tations trans it whene&er the" ha&e data to sendDetect collision or wait for acknowledg ent7f no acknowledg ent (or collision), tr" again after a

rando waiting ti e

Collision4 7f ore than one node trans its at thesa e ti e

7f there is a collision, all nodes ha&e to re8trans it/ackets

Al h 3 l d Al h


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Mechanis – rando , distri!uted (no central ar!iter), ti e8 ulti/le: – 'lotted Aloha additionall" uses ti e8slots, sending ust

alwa"s start at slot !oundaries

Aloha

'lotted Aloha

Aloha3slotted Aloha

sender A

sender $sender C

collision

sender Asender $

sender C

collision

t

t

'l tt d Al h


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'lotted Aloha

Ti e is di&ided into slots – slot = one packet transmission time at least Master station generates synchronization

pulses for ti e8slots'tation waits till !eginning of slot to trans it

Vulnerability Window reduced fro T to Tgoodput dou!les


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$it l & l d t ti 3 ti


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$it le&el error detection3correction

'ingle8!it, ulti8!it or !urst errors introduceddue to channel noise – Detected using redundant infor ation sent along

with dataFull #edundanc"4 – 'end e&er"thing twice – 'i /le !ut inefficientCo on 'che es4

– 6arit" – C"clic #edundanc" Check (C#C) – Checksu

9 d t ti /


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9rror detection /rocess

Trans itter – For a gi&en fra e, an error8detecting code (check !its)is calculated fro data !its

– Check !its are a//ended to data !its

#ecei&er – 'e/arates inco ing fra e into data !its and check!its

– Calculates check !its fro recei&ed data !its

– Co /ares calculated check !its against recei&edcheck !its – Detected error occurs if is atch


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Fra e le&el error correction

6ro!le s in trans itting a se%uence of fra eso&er a loss" link – fra e da age, loss, reordering, du/lication, insertion

'olutions4 – Forward 9rror Correction (F9C)

= Hse of redundanc" for /acket le&el error correction= $lock Codes, Tur!o Codes

– Auto atic #e/eat #e%uest (A#1)= Hse of acknowledge ents and retrans ission= 'to/ and Wait 'liding Window

$lock Code (9rror Correction)


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$lock Code (9rror Correction);a ing distance – for n8!it !inar" se%uences, the nu !er ofdifferent !its

– 9-g-, &. G+..+.. & G..+++. d(&., & )G<For each data !lock, create a codeword'end the codeword7f the code is in&alid, look for data with shortest ha ing distance(/ossi!l" correct code)

Data!lock (kG ) Codeword (nG@)++ ++++++. ++....+ ..++... ....+

'u//ose "ou recei&e codeword ++.++ (error)Closest is +++++ (onl" one !it different)

9fficient &ersion4 Tur!o Codes


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'to/ and Wait A#1'ender waits for AC>(acknowledge ent) aftertrans itting each fra e kee/sco/" of last fra e-#ecei&er sends AC> if recei&ed

fra e is error free-'ender retrans its fra e if

AC>not recei&ed !efore ti ere:/ires-

'i /le to i /le ent !ut a"waste !andwidth-

9fficient 0ersion4 'liding Window


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$andwidth and Dela"

$andwidth


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$andwidth

A ount of data that can !e trans itted /er unit ti e – e:/ressed in c"cles /er second, or ;ertE (;E) for analog

de&ices – e:/ressed in !its /er second (!/s) for digital de&ices –

>$ G U.+ !"tes M!/s G .+U2 !/s

Link &3s 9nd8to89nd

$andwidth &3s !it width


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$andwidth &3s !it width

Latenc" (dela")


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Latenc (dela )

Ti e it takes to send essage fro /oint A to /oint $ – Latenc" G 6ro/agation Trans it

1ueue – 6ro/agation G Distance 3

'/eedOfLight

– Trans it G 'iEe 3 $andwidth

1ueueing not rele&ant for direct links$andwidth not rele&ant if 'iEe G . !it'oftware o&erhead can do inate when Distance is s all

#TT4 round8tri/ ti e

Dela" X $andwidth /roduct


74/298


Dela X $andwidth /roduct

#elati&e i /ortance of !andwidth and dela"

' all essage4 . s &s .++ s do inates.M!/s &s .++M!/s

Large essage4 .M!/s &s .++M!/s do inates. s &s .++ s


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76/298

TC6376 $asics


77/298

' it h d t k


78/298


'witched networks


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TC6376 la"ers

6h"sical La"er4 – Trans itting !its o&er a channel- – Deals with electrical and /rocedural interface to the

trans ission ediu -

Data Link La"er4 – Transfor the raw /h"sical la"er into a Vlink for the

higher la"er- – Deals with fra ing, error detection, correction and

ulti/le access-


80/298


TC6376 la"ers (contd-)

Network La"er4 – Addressing and routing of /ackets- – Deals with su!netting, route deter ination -

Trans/ort La"er4 – end8to8end connection characteristics- – Deals with retrans issions, se%uencing and

congestion control-

TC6376 la"ers (contd )


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TC6376 la ers (contd-)

A//lication La"er4 – VVa//lication /rotocols- – Deals with /ro&iding ser&ices to users and a//lication

de&elo/ers-

6rotocols are the !uilding !locks of a network

architecture-

Lower la"er ser&ices


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Lower la er ser&icesHnacknowledged connectionless ser&ice – No acknowledge ents, no connection – 9rror reco&er" u/ to higher la"ers – For low error8rate links or &oice traffic

Acknowledged connectionless ser&ice – Acknowledge ents i /ro&e relia!ilit" – For unrelia!le channels- e-g-4 wireless s"ste s

Acknowledged connection8oriented ser&ice – 9%ui&alent of relia!le !it8strea in8order deli&er" – Connection esta!lish ent and release – 7nter8router traffic

h


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5eneric router architecture

LookupIP Address UpdateHeader

Header Processing

AddressTable

AddressTable

LookupIP Address UpdateHeader

Header Processing

AddressTable

AddressTable

LookupIP Address

UpdateHeader

Header Processing

AddressTable

AddressTable

QueuePacket

BufferMemory

BufferMemory

QueuePacket

BufferMemory

BufferMemory

QueuePacket

BufferMemory

BufferMemory

Data Hdr

Data Hdr

Data Hdr

!

"

!

"

" times line rate

" times line rate

T"/ical TC6 !eha&iour


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!

"

#

$

%

%!%"

% ! & " ' # ( $

Time (round trips)

C o n g e s t i o n W i n d o w s i z e

( s e g m e n t s )

Slow start

Congestionavoidance

Slow startthreshold

T /ical TC6 !eha&iour

'low start /hase


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low start /hase

= initialiEe4= Cwnd G .

= for (each AC>)

= Cwnd= until

= loss detection O#

=Cwnd R ssthresh

;ost A

o n e s e ) m e n t # T T

;ost $

time

t w o s e ) m e n t s

* o +r s e ) m e n t s

Congestion a&oidance /hase


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Congestion a&oidance /hase

3J Cwnd R threshold J3= Hntil (loss detection) B e&er" w AC>s4 Cwnd = ssthresh G Cwnd3= Cwnd G .= /erfor slow start

1

;ost A ;ost $

time

# T T

* o +r s e ) m e n t s

* i v e s e ) m e nt s

TC64 Fast retrans it and Fast reco&er"


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!

"

#

$

%

Time (round trips)

W i n d o w s i z e ( s e g m e n t s )

advertised window

,*ter *ast recover

TC64 Fast retrans it and Fast reco&er


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*+ -.. (WiFi) O&er&iew

Wireless LANs


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Wireless LANs

7nfrared (7rDA) or radio links (Wa&elan) Ad&antages – &er" fle:i!le within the rece/tion area – Ad8hoc networks /ossi!le – (al ost) no wiring difficultiesDisad&antages – low !andwidth co /ared to wired networks – an" /ro/rietar" solutions

7nfrastructure &3s ad8hoc networks (*+ -..)

7nfrastructure &s- Ad hoc networks


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infrastructure network

ad8hoc network

A6 A6

A6

wired network

A64 Access 6oint

'ource4 'chiller

Difference !etween wired and wireless


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Difference !etween wired and wireless

7f !oth A and C sense the channel to !e idle at the sa e

ti e, the" send at the sa e ti e-Collision can !e detected at sender in 9thernet-;alf8du/le: radios in wireless cannot detect collision atsender-

, . /,

.

/

0t1ernet 2,3 4ireless 2,3

Carrier 'ense Multi/le Access (C'MA)


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Carrier 'ense Multi/le Access (C'MA)

Listen !efore "ou s/eakCheck whether the ediu is acti&e !efore sending a/acket (i-e carrier sensing )7f ediu idle, then trans it

7f collision ha//ens, then detect and resol&e

7f ediu is found !us", trans ission follows4 – .8 /ersistent – 68 /ersistent – Non8/ersistent

C lli i d i (C'MA3CD)


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Collision detection (C'MA3CD)

All afore entioned sche e can suffer fro collisionDe&ice can detect collision – Listen while trans itting – Wait for J /ro/agation dela"

On collision detection wait for rando ti e !eforeretr"ing$inar" 9:/onential $ackoff Algorith – #educes the chances of two waiting stations /icking the

sa e rando ti e

$i " 9 / ti l $ k ff


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$inar" 9:/onential $ackoff

.-On detecting . st collision for /acket : station A chooses a nu !er r !etween + and .- wait for r J slot ti e and trans it-'lot ti e is taken as J /ro/agation dela"k- On detecting k th collision for /acket : choose r !etween +,.,--,( k –.)

When &alue of k !eco es high (.+), gi&e u/-#ando iEation increase with larger window, !ut dela"increases-

;idden Ter inal 6ro!le


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– A and C cannot hear each other- – A sends to $, C cannot recei&e A- – C wants to send to $, C senses a Kfree ediu

(C' fails) – Collision occurs at $- – A cannot recei&e the collision (CD fails)- – A is Khidden for C-

;

., /

Effectofinterferencerange


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Effect of interference range

Transmission #rom 1 ⇒ 2 )i"" #ai"

'olution for ;idden Ter inals


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olution for ;idden Ter inals A first sends a Request-to-Send R!S" to $On recei&ing #T' , $ res/onds #lear-to-Send #!S";idden node C o&erhears CT' and kee/s %uiet – Transfer duration is included in !oth #T' and CT'

9:/osed node o&erhears a #T' !ut not the CT' – D s trans ission cannot interfere at $

, . /R56

/56 /56

D,5,

DR56

Co /onents of 7999 *+ -


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Co /onents of 7999 + ..architecture

The !asic ser&ice set ($'') is the !asic !uilding!lock of an 7999 *+ -.. LANThe o&als can !e thought of as the co&erage areawithin which e !er stations can directl"co unicateThe 7nde/endent $'' (7$'') is the si /lest LAN- 7t

a" consist of as few as two stationsad-1oc network BSS2BSS1

*+ -.. 8 ad8hoc network (DCF)


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( )

Direct co unicationwithin a li ited range – 'tation ('TA)4

ter inal with accessechanis s to thewireless ediu

– $asic 'er&ice 'et ($'')4grou/ of stations using the

sa e radio fre%uenc"

$%&'(( )*+

$''

$%&'(( )*+

$'' .'TA .

'TA ?

'TA @

'TA

'TA <

'ource4 'chiller

*+ -.. 8 infrastructure network (6CF)


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Distri!ution '"ste

6ortal

$%&', )*+

Access 6oint

$%&'(( )*+

$''

$%&'(( )*+

$'' . Access

6oint

( )'tation ('TA) – ter inal with access echanis s

to the wireless ediu and radiocontact to the access /oint$asic 'er&ice 'et ($'') – grou/ of stations using the sa e

radio fre%uenc" Access 6oint

– station integrated into thewireless LAN and the distri!utions"ste

6ortal – !ridge to other (wired) networksDistri!ution '"ste – interconnection network to for

one logical network (99'49:tended 'er&ice 'et) !asedon se&eral $''

'TA .

'TA 'TA <

9''

'ource4 'chiller

*+ -..8 in the TC6376 stack


101/298


o!ile ter inal

access /oint

ser&er

fi:ed ter inal

a//lication

TC6

*+ -.. 6;Y

*+ -.. MAC

76

*+ -< MAC

*+ -< 6;Y

a//lication

TC6

*+ -< 6;Y

*+ -< MAC

76

*+ -.. MAC

*+ -.. 6;Y

LLC


LLC LLC

*+ -.. 8 MAC la"er


102/298


Traffic ser&ices – As"nchronous Data 'er&ice ( andator") – DCF – Ti e8$ounded 'er&ice (o/tional) 8 6CF

Access ethods – DCF C'MA3CA ( andator")

= collision a&oidance &ia rando iEed !ack8off echanis= AC> /acket for acknowledge ents (not for !roadcasts)

– DCF w3 #T'3CT' (o/tional)=

a&oids hidden ter inal /ro!le – 6CF (o/tional)= access /oint /olls ter inals according to a list

*+ -.. 8 C'MA3CA


103/298


t

ediu !us"

D7F'D7F'

ne:t fra e

contention window(rando iEed !ack8off

echanis )

– station read" to send starts sensing the ediu (Carrier 'ense!ased on CCA, Clear Channel Assess ent)

– if the ediu is free for the duration of an 7nter8Fra e '/ace(7F'), the station can start sending (7F' de/ends on ser&ice t"/e)

– if the ediu is !us", the station has to wait for a free 7F', then

the station ust additionall" wait a rando !ack8off ti e (collisiona&oidance, ulti/le of slot8ti e) – if another station occu/ies the ediu during the !ack8off ti e of

the station, the !ack8off ti er sto/s (fairness)

slot ti edirect access if

ediu is free ≥ D7F'

*+ -.. –C'MA3CA e:a /le


104/298


t

!us"

!o e

station .

station

station <

station ?

station @

/acket arri&al at MAC

D7F'!o e

!o e

!o e

!us"

ela/sed !ackoff ti e

!o r residual !ackoff ti e

!us" ediu not idle (fra e, ack etc-)

!o r

!o r D7F'

!o e

!o e

!o e !o r D7F'

!us"

!us"

D7F'!o e !us"

!o e

!o e

!o r

!o r

*+ -.. –#T'3CT'


105/298


station can send #T' with reser&ation /ara eter after waiting for D7F'(reser&ation deter ines a ount of ti e the data /acket needs the

ediu )acknowledge ent &ia CT' after '7F' !" recei&er (if read" to recei&e)sender can now send data at once, acknowledge ent &ia AC>other stations store ediu reser&ations distri!uted &ia #T' and CT'

t

'7F'

D7F'

data

AC>

defer access

other stations

recei&er

sender data

D7F'

contention

#T'

CT''7F' '7F'

NA0 (#T')NA0 (CT')

*+ -.. 8 6CF 7


106/298


67F'

stationsZNA0

wirelessstations

/ointcoordinator

D.

H.'7F'

NA0

'7F'D

H'7F'

'7F'

'u/erFra et+

ediu !us"

t.

*+ -.. 8 6CF 77


107/298


tstationsZNA0

wirelessstations

/ointcoordinator

D<

NA0

67F'D?

H?'7F'

'7F'CF end

contention/eriod

contention free /eriod

t t< t?

CF6 structure and Ti ing


108/298


*+ -.. 8 MAC anage ent


109/298


'"nchroniEation – tr" to find a LAN, tr" to sta" within a LAN – ti er etc-

6ower anage ent – slee/8 ode without issing a essage

– /eriodic slee/, fra e !uffering, traffic easure ents Association3#eassociation

– integration into a LAN – roa ing, i-e- change networks !" changing access /oints

– scanning, i-e- acti&e search for a networkM7$ 8 Manage ent 7nfor ation $ase – anaging, read, write

*+ -.. 8 Channels, association


110/298


*+ -..!4 -?5;E8 -?*@5;E s/ectru di&ided into ..channels at different fre%uencies – A6 ad in chooses fre%uenc" for A6 – interference /ossi!le4 channel can !e sa e as that

chosen !" neigh!oring A6P

host4 ust associate with an A6 – scans channels, listening for beacon rames containing

A6 s na e (''7D) and MAC address

– selects A6 to associate with – a" /erfor authentication – will t"/icall" run D;C6 to get 76 address in A6 s su!net

*+ -.. &ariants


111/298


M,/

MI.

D666 78 IR98

409

22/

M,/M mt

$ !;%%<' %% M


112/298

6u!lic WLANs


113/298


6ro&ide significantl" higher data rates than wide8area wireless networksCould take ad&antages of !oth WLAN and wide8

area radio technologies to create new ser&icesand reduce networking costs6u!lic WLANs are the first wa&e of all876 radioaccess networksNew and inno&ati&e !usiness odels for/ro&iding /u!lic o!ile ser&ices

Worldwide WLAN sales


114/298



115/298

*+ -.2 (WiMaX) O&er&iew

Moti&ation for *+ -.2


116/298


$road!and4 – A trans ission facilit" ha&ing a !andwidth sufficient tocarr" ulti/le &oice, &ideo or data, si ultaneousl"-

– ;igh8ca/acit" fi!er to e&er" user is e:/ensi&e-

$road!and Wireless Access4 – /ro&ides KFirst8 ile network access to !uildings- – Cost effecti&e and eas" de/lo" ent-

7999 *+ -.2


117/298


WirelessMAN air interface – for fi:ed /oint to ulti8/oint $WA

$road !andwidth4 .+822 5;E

– Channel as wide as * M;E and – Data rate u/to .


118/298


Channel odel


119/298


Two Channels4 Downlink and H/link'u//orts !oth Ti e Di&ision Du/le:ing andFre%uenc" Di&ision Du/le:ing

$ase station a/s downstrea traffic onto ti eslots with indi&idual su!scri!er stations allocatedti e slot seriall"

H/link is shared !etween a nu !er of su!scri!erstations !" Ti e Di&ision Multi/le Access

Network initialiEation of ''


120/298


Ac%uires downlink and u/link channel-6erfor initial ranging, negotiate !asic ca/a!ilities-6erfor registration and authoriEation-

9sta!lish 76 connecti&it" and ti e of da"-Transfer o/erational /ara eters-'et u/ connections-

$andwidth re%uests and grants


121/298


Wa"s – $andwidth re%uest /acket- – 6igg"!acking !andwidth re%uest with nor al data

/acket-#e%uest can !e ade during ti e slot assigned !" !asestation for sending re%uest or data-5rant odes – 5rant /er connection- – 5rant /er su!scri!er station-5rant /er su!scri!er station is ore efficient and scala!le!ut co /le: than 5rant /er connection-

H/link scheduling ser&ices


122/298


Hnsolicited grant ser&ice – 'u//ort a//lications generating constant !it rate traffic /eriodicall"- – 6ro&ides fi:ed !andwidth at /eriodic inter&als-

#eal8ti e /olling ser&ice – 'u//orts real8ti e a//lications generating &aria!le !it rate traffic

/eriodicall"- – Offers /eriodic o//ortunities to re%uest !andwidth-

Non8real8ti e /olling ser&ice – 'u//orts non8real8ti e a//lications generating &aria!le !it rate

traffic regularl"- – Offers o//ortunities to re%uest !andwidth regularl"-

$est effort – Offers no guarantee-

802.16: Summary


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8i 1er t1ro+ 1p+t at lon er ran es ( u/ to @+ k ) – $etter !its3second3;E at longer ranges

6cala


124/298


$ !;%# $ !;%#a R0Bd $ !;%#e

/ompleted Dec ! % $ !;%#a: Ean ! &$ !;%#R0Bd: @&F "

0stimate ! #

6pectr+m % - ## G8 H %% G8 H # G8

/1annel /onditions 2ine o* si 1t onl 3on line o* si 1t 3on line o* si 1t

.it Rate &! %&" M


125/298

*+ -.. 7nternals

Wireless LANs &s- Wired LANs


126/298


Destination address does not e%ual destinationlocationThe edia i /act the design – wireless LANs intended to co&er reasona!le

geogra/hic distances ust !e !uilt fro !asicco&erage !locks7 /act of handling o!ile (and /orta!le)stations

– 6ro/agation effects – Mo!ilit" anage ent – 6ower anage ent

Wireless Media


127/298


6h"sical la"ers used in wireless networks – ha&e neither a!solute nor readil" o!ser&a!le !oundaries

outside which stations are una!le to recei&e fra es – are un/rotected fro outside signals – co unicate o&er a ediu significantl" less relia!le

than the ca!le of a wired network – ha&e d"na ic to/ologies – lack full connecti&it" and therefore the assu /tion

nor all" ade that e&er" station can hear e&er" other

station in a LAN is in&alid (i-e-, 'TAs a" !e Khidden fro each other) – ha&e ti e &ar"ing and as" etric /ro/agation /ro/erties

7nfrastructure &s- Ad hoc WLANsi f t t


128/298



ad8hoc network

A6 A6

A6

wired network

A64 Access 6oint

'ource4 'chiller


129/298

*+ -..8 in the TC6376 stack


130/298


o!ile ter inal

access /oint

ser&er

fi:ed ter inal

a//lication

TC6

*+ -.. 6;Y

*+ -.. MAC

76

*+ -< MAC

*+ -< 6;Y

a//lication

TC6

*+ -< 6;Y

*+ -< MAC

76

*+ -.. MAC

*+ -.. 6;Y

LLC


LLC LLC

Functional Diagra


131/298


*+ -.. 8 La"ers and functions


132/298


6LC6 6h"sical La"erCon&ergence 6rotocol – clear channel assess ent

signal (carrier sense)6MD 6h"sical MediuDe/endent – odulation, coding6;Y Manage ent – channel selection, M7$'tation Manage ent – coordination of all

anage ent functions

6MD

6LC6

MAC

LLC

MAC Manage ent

6;Y Manage ent

MAC – access echanis s,

frag entation, encr"/tionMAC Manage ent

– s"nchroniEation, roa ing,M7$, /ower anage ent

6 ; Y

D L C

' t a t i o n

M a n a g e e n

t

*+ -.. 8 infrastructure network( )


133/298


Distri!ution '"ste

6ortal

$%&', )*+

Access 6oint

$%&'(( )*+

$''

$%&'(( )*+

$'' . Access

6oint

'tation ('TA) – ter inal with access echanis s

to the wireless ediu and radiocontact to the access /oint

$asic 'er&ice 'et ($'') – grou/ of stations using the sa e

radio fre%uenc" Access 6oint

– station integrated into thewireless LAN and the distri!utions"ste

6ortal – !ridge to other (wired) networksDistri!ution '"ste

– interconnection network to forone logical network (99'49:tended 'er&ice 'et) !asedon se&eral $''

'TA .

'TA 'TA <

9''

'ource4 'chiller

Distri!ution '"ste (D') conce/ts


134/298


( )

The Distri!ution s"ste interconnects ulti/le $''s*+ -.. standard logicall" se/arates the wirelessediu fro the distri!ution s"ste – it does not

/reclude, nor de and, that the ulti/le edia !esa e or different

An Access 6oint (A6) is a 'TA that /ro&ides accessto the D' !" /ro&iding D' ser&ices in addition toacting as a 'TA-Data o&es !etween $'' and the D' &ia an A6

The D' and $''s allow *+ -.. to create a wirelessnetwork of ar!itrar" siEe and co /le:it" called the9:tended 'er&ice 'et network (9'')


135/298

*+ -.. 8 6h"sical la"er


136/298


< &ersions of s/read s/ectru 4 radio (t"/- -? 5;E), . 7# – data rates . or M!/sF;'' (Fre%uenc" ;o//ing '/read '/ectru ) – s/reading, des/reading, signal strength, t"/icall" . M!/s – in- -@ fre%uenc" ho/s3s (H'A), two8le&el 5F'> odulationD''' (Direct 'e%uence '/read '/ectru ) – D$6'> odulation for . M!/s (Differential $inar" 6hase 'hift

>e"ing), D16'> for M!/s (Differential 1uadrature 6'>) – /rea !le and header of a fra e is alwa"s trans itted with . M!/s,

rest of trans ission . or M!/s – chi//ing se%uence4 ., 8., ., ., 8., ., ., ., 8., 8., 8. ($arker

code)

– a:- radiated /ower . W (H'A), .++ W (9H), in- . W7nfrared – *@+8 @+ n , diffuse light, t"/- .+ range – carrier detection, energ" detection, s"nchroniEation

'/read8s/ectru co unications


137/298


'ource4 7ntersil


138/298


139/298

*+ -.. 8 MAC la"er


140/298


Traffic ser&ices – As"nchronous Data 'er&ice ( andator") – DCF – Ti e8$ounded 'er&ice (o/tional) 8 6CF

Access ethods

– DCF C'MA3CA ( andator")= collision a&oidance &ia rando iEed !ack8off echanis= AC> /acket for acknowledge ents (not for !roadcasts)

– DCF w3 #T'3CT' (o/tional)= a&oids hidden3e:/osed ter inal /ro!le , /ro&ides

relia!ilit" – 6CF (o/tional)= access /oint /olls ter inals according to a list

contention windowff

*+ -.. 8 C'MA3CA


141/298


t

ediu !us"

D7F'D7F'

ne:t fra e

(rando iEed !ack8off echanis )

– station which has data to send starts sensing the ediu (Carrier'ense !ased on CCA, Clear Channel Assess ent) – if the ediu is free for the duration of an 7nter8Fra e '/ace

(7F'), the station can start sending (7F' de/ends on ser&ice t"/e) – if the ediu is !us", the station has to wait for a free 7F' /lus an

additional rando !ack8off ti e ( ulti/le of slot8ti e) – if another station occu/ies the ediu during the !ack8off ti e ofthe station, the !ack8off ti er sto/s (fairness)

slot ti edirect access if

ediu is free ≥ D7F'

*+ -.. DCF – !asic access


142/298


7f ediu is free for D7F' ti e, station sends data

recei&ers acknowledge at once (after waiting for '7F') if the /acketwas recei&ed correctl" (C#C)auto atic retrans ission of data /ackets in case of trans issionerrors

t

'7F'

D7F'

data

AC>

waiting ti e

other stations

recei&er

sender data

D7F'

contention

*+ -.. –#T'3CT'


143/298


7f ediu is free for D7F', station can send #T' with reser&ation/ara eter (reser&ation deter ines a ount of ti e the data /acket needsthe ediu )acknowledge ent &ia CT' after '7F' !" recei&er (if read" to recei&e)sender can now send data at once, acknowledge ent &ia AC>other stations store ediu reser&ations distri!uted &ia #T' and CT'

t

'7F'

D7F'

data

AC>

defer access

other stations

recei&er

sender data

D7F'

contention

#T'

CT''7F' '7F'

NA0 (#T')NA0 (CT')

*+ -.. 8 Carrier 'ensing


144/298


In I000 $ !;%% carrier sensin is per*ormed

– at the air interface ( physical carrier sensing ), and – at the MAC la"er ( .irtual carrier sensing )91 sical carrier sensin – detects /resence of other users !" anal"Eing all detected

/ackets – Detects acti&it" in the channel &ia relati&e signal strength

fro other sourcesBirt+al carrier sensin is done !" sending M6DH durationinfor ation in the header of #T'3CT' and data fra esChannel is !us" if eit1er echanis s indicate it to !e

Duration field indicates the a ount of ti e (in icroseconds)re%uired to co /lete fra e trans ission'tations in the $'' use the infor ation in the duration field toadSust their network allocation &ector (NA0)

*+ -.. 8 Collision A&oidance


145/298


7f ediu is not free during D7F' ti e--

5o into Collision A&oidance4 Once channel !eco esidle, wait for D7F' ti e /lus a rando l" chosen!ackoff ti e !efore atte /ting to trans itFor DCF the !ackoff is chosen as follows4

– When first trans itting a /acket, choose a !ackoff inter&al inthe range [+, cw\ cw is contention window, no inall"


146/298


data

wait$. G @

$ G .@

$. G @

$ G +

data

wait

.% and .! are


147/298


t

!us"

!o e

station .

station

station <

station ?

station @

/acket arri&al at MAC

D7F'!o e

!o e

!o e

!us"

ela/sed !ackoff ti e

!o r residual !ackoff ti e

!us" ediu not idle (fra e, ack etc-)

!o r

!o r D7F'

!o e

!o e

!o e !o r D7F'

!us"

!us"

D7F'!o e !us"

!o e

!o e

!o r

!o r

'ource4 'chiller

*+ -.. 8 6riorities


148/298


defined through different inter fra e s/aces – andator" idleti e inter&als !etween the trans ission of fra es'7F' ('hort 7nter Fra e '/acing) – highest /riorit", for AC>, CT', /olling res/onse – '7F'Ti e and 'lotTi e are fi:ed /er 6;Y la"er (.+ µs and +

µs res/ecti&el" in D''')67F' (6CF 7F') – ediu /riorit", for ti e8!ounded ser&ice using 6CF – 67F'Ti e G '7F'Ti e 'lotTi eD7F' (DCF 7F') – lowest /riorit", for as"nchronous data ser&ice – DCF87F'4 D7F'Ti e G '7F'Ti e :'lotTi e

'olution to ;idden Ter inals


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A first sends a Request-to-Send R!S" to $On recei&ing #T' , $ res/onds #lear-to-Send #!S";idden node C o&erhears CT' and kee/s %uiet – Transfer duration is included in !oth #T' and CT'

9:/osed node o&erhears a #T' !ut not the CT' – D s trans ission cannot interfere at $

, . /R56/56 /56

D,5,

DR56

*+ -.. 8 #elia!ilit"

H k l d t


150/298


Hse acknowledge ents – When $ recei&es DATA fro A, $ sends an AC> – 7f A fails to recei&e an AC> , A retrans its the DATA – $oth C and D re ain %uiet until AC> (to /re&ent collision of

AC> ) – 9:/ected duration of trans ission AC> is included in

#T'3CT' /ackets

, . /R56

/56 /56

D,5,

DR56

,/J

*+ -.. 8 Congestion Control


151/298


Contention window (cw) in DCF4 Congestioncontrol achie&ed !" d"na icall" choosing cwlarge cw leads to larger !ackoff inter&alssmall cw leads to larger nu !er of collisions

$inar" 9:/onential $ackoff in DCF4 – When a node fails to recei&e CT' in res/onse to

its #T' , it increases the contention window= cw is dou!led (u/ to a !ound cw a: G.+ < )

– H/on successful co /letion data transfer, restorecw to cw inG


152/298


t

'7F'

D7F'

data

AC> .

other stations

recei&er

sender frag .

D7F'

contention

#T'

CT''7F' '7F'

NA0 (#T')NA0 (CT')

NA0 (frag . )NA0 (AC> . )

'7F' AC>

frag

'7F'

*+ -.. 8 MAC anage ent


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'"nchroniEation

– tr" to find a LAN, tr" to sta" within a LAN – ti er etc-

6ower anage ent – slee/8 ode without issing a essage

– /eriodic slee/, fra e !uffering, traffic easure ents Association3#eassociation

– integration into a LAN – roa ing, i-e- change networks !" changing access /oints – scanning, i-e- acti&e search for a network

M7$ 8 Manage ent 7nfor ation $ase – anaging, read, write


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'"nchroniEation using a $eacon(infrastructure ode)


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!eacon inter&al

tediu

access/oint!us"

$

!us" !us" !us"

$ $ $

&alue of the ti esta / $ !eacon fra e

'ource4 'chiller

'"nchroniEation using a $eacon(ad8hoc ode)


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tediu

station.

!us"

$ .

!eacon inter&al

!us" !us" !us"

$ .

&alue of the ti esta / $ !eacon fra e

station$ $

rando dela"

*+ -.. 8 6ower anage ent7dea4 switch the transcei&er off if not needed


157/298


7dea4 switch the transcei&er off if not needed'tates of a station4 slee/ and awakeTi ing '"nchroniEation Function (T'F) – stations wake u/ at the sa e ti e7nfrastructure – Traffic 7ndication Ma/ (T7M)

= list of unicast recei&ers trans itted !" A6 – Deli&er" Traffic 7ndication Ma/ (DT7M)

= list of !roadcast3 ulticast recei&ers trans itted !" A6 Ad8hoc

– Ad8hoc Traffic 7ndication Ma/ (AT7M)= announce ent of recei&ers !" stations !uffering fra es= ore co /licated 8 no central A6= collision of AT7Ms /ossi!le (scala!ilit" )

*+ -.. 8 9nerg" Conser&ation


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6ower 'a&ing in infrastructure ode – Nodes can go into slee/ or stand!" ode – An Access 6oint /eriodicall" trans its a !eacon

indicating which nodes ha&e /ackets waiting for the

– 9ach /ower sa&ing (6') node wakes u/ /eriodicall"to recei&e the !eacon

– 7f a node has a /acket waiting, then it sends a 6'86oll

= After waiting for a !ackoff inter&al in [ +,CW in \ – Access 6oint sends the data in res/onse to 6'8/oll

6ower sa&ing with wake8u/ /atterns(infrastructure)


159/298


(infrastructure)T7M inter&al

t

ediu

access/oint

!us"

D

!us" !us" !us"

T T D

T T7M D DT7M

DT7M inter&al

$$

$ !roadcast3 ulticast

station

awake

/ 6' /oll

/

d

d

d data trans issionto3fro the station

'ource4 'chiller

6ower sa&ing with wake8u/ /atterns(ad8hoc)


160/298


(ad8hoc)

awake

A trans it AT7M D trans it datat

station .$ . $ .

$ !eacon fra e

station$ $

rando dela"

A

a

D

d

AT7Mwindow !eacon inter&al

a acknowledge AT7M d acknowledge data

*+ -.. 8 Fra e for atT"/es


161/298


T"/es – control fra es, anage ent fra es, data fra es'e%uence nu !ers – i /ortant against du/licated fra es due to lost AC>s

Addresses – recei&er, trans itter (/h"sical), $'' identifier, sender (logical)

Miscellaneous – sending ti e, checksu , fra e control, data

Fra eControl

Duration7D

Address.

Address Address<

'e%uenceControl

Address? Data C#C

2 2 2 2 ?+8


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fra econtrol duration

address.

address address?

address< /a"load C#C

2 2 2 2 + 8


163/298


Internetrouter

AP

H #

AP MA% addr H MA% addr # MA% addraddress . address address <

*+!, 11 frame

# MA% addr AP MA% addrdest- address source address

*+!, 3 frame

*+ -.. fra e4 oreframe se1 2


164/298


fra econtrol duration

address.

address address?

address< /a"load C#C

2 2 2 2 + 8


165/298


Control Fra es – #T'3CT'3AC> – CF86oll3CF89nd

Manage ent Fra es

– $eacons – 6ro!e #e%uest3#es/onse – Association #e%uest3#es/onse – Dissociation3#eassociation – Authentication3Deauthentication – AT7M

Data Fra es

*+ -.. 8 #oa ing

$ad connection in 7nfrastr ct re ode 6erfor 4


166/298


$ad connection in 7nfrastructure ode 6erfor 4scanning of en&iron ent – listen into the ediu for !eacon signals or send /ro!es into the

ediu and wait for an answer send #eassociation #e%uest – station sends a re%uest to a new A6(s)recei&e #eassociation #es/onse – success4 A6 has answered, station can now /artici/ate – failure4 continue scanning

A6 acce/ts #eassociation #e%uest and – signals the new station to the distri!ution s"ste – the distri!ution s"ste u/dates its data !ase (i-e-, location

infor ation) – t"/icall", the distri!ution s"ste now infor s the old A6 so it can

release resources

*+ -.. 8 #oa ing within sa e su!net


167/298


'ub ors&itc'

AP !

AP

HBB. !

BB.

router;. re ains in sa e 76su!net4 76 address canre ain sa eswitch4 which A6 isassociated with ;. – self8learning – switch will see fra e fro ;.

and Kre e !er which switch/ort can !e used to reach ;.

*+ -.. 8 6oint Coordination Function


168/298


Coe:istence of 6CF and DCFA 6oint Coordinator (6C) resides in the Access 6oint and


169/298


A 6oint Coordinator (6C) resides in the Access 6oint andcontrols fra e transfers during a Contention Free 6eriod(CF6)

A CF86oll fra e is used !" the 6C to in&ite a station tosend data- 'tations are /olled fro a list aintained !"the 6C

The CF6 alternates with a Contention 6eriod (C6) inwhich data transfers ha//en as /er the rules of DCFThis C6 ust !e large enough to send at least one

a:i u 8siEed /acket including #T'3CT'3AC>CF6s are generated at the CF6 re/etition rate

The 6C sends $eacons at regular inter&als and at thestart of each CF6The CF89nd fra e signals the end of the CF6

CF6 structure and Ti ing


170/298


*+ -.. 8 6CF 7


171/298


67F'

stationsZNA0

wirelessstations

/oint

coordinator

D.

H.'7F'

NA0

'7F'D

H'7F'

'7F'

'u/erFra et+

ediu !us"

t.

'ource4 'chiller

*+ -.. 8 6CF 77


172/298


tstationsZNA0

wirelessstations

/ointcoordinator

D<

NA0

67F'D?

H?'7F'

'7F'CF end

contention/eriod

contention free /eriod

t t< t?


173/298


174/298

Sridhar Iyer IIT Bombay 1747CCC ++


175/298


176/298

Channel selection (non8o&erla//ing)9uro/e (9T'7)


177/298


?++[M;E\

?. ?*


178/298


– Hser through/ut (.@++ !"te /ackets)4 @-< (2),.* ( ?), ? (


179/298


rate ser&ice /a"load

&aria!le !its

2 M!it3s

6LC6 /rea !le signal data

s" !ols. . &aria!le

reser&ed length tail/arit" tail /ad

2.22...? &aria!le

2, , . , .*, ?,


180/298


@ ( )

?* data ? /ilot


181/298


@.@+ [M;E\@.*+ @


182/298


– 9nhance the current *+ -.. MAC to e:/and su//ortfor a//lications with 1ualit" of 'er&ice re%uire ents,and in the ca/a!ilities and efficienc" of the /rotocol-

9DCF – Contention Window !ased /rioritiEation= #eal8ti e= $est effort

– 0irtual collision resol&ed in fa&or of higher /riorit"

Extending DCF: EDCF

EDCF improves upon DCF by


183/298


EDCF improves upon DCF byprioritising trafcEach trafc class can have adi erent contention windowDi erent trafc classes touse di erent inter ramespaces, called rbitration!nter rame "pace # !F"$

EDCF contention windowparameters%o!& #priority$: '()*F+& w o priority: )-(*.-)%o!& w o priority:)-(*.-)

ccessto

channel

FTP fows + unprioritisedVoIP: larger contentionwindow

Prioritised VoIP calls : smallercontention window

7999 *+ -.. 'u ar"


184/298


7nfrastructure and ad hoc odes using DCFCarrier 'ense Multi/le Access$inar" e:/onential !ackoff for collision a&oidance andcongestion control

Acknowledge ents for relia!ilit"6ower sa&e ode for energ" conser&ationTi e8!ound ser&ice using 6CF'ignaling /ackets for a&oiding 9:/osed3;idden ter inal/ro!le s, and for reser&ation – Mediu is reser&ed for the duration of the trans ission – #T'8CT' in DCF – 6olls in 6CF


185/298


Mo!ile 76

Traditional #outing

A routing protocol sets u/ a routing table in routers


186/298


#outing /rotocol is t"/icall" !ased on Distance80ector orLink8'tate algorith s

#outing and Mo!ilit"

Finding a /ath fro a source to a destination


187/298


Finding a /ath fro a source to a destination

7ssues – Fre%uent route changes

= a ount of data transferred !etween route changes a"

!e uch s aller than traditional networks – #oute changes a" !e related to host o&e ent – Low !andwidth links

5oal of routing /rotocols – decrease routing8related o&erhead – find short routes – find Ksta!le routes (des/ite o!ilit")

Mo!ile 76 (#FC


188/298


– !ased on 76 address network /refi: deter ines the su!net

– change of /h"sical su!net i /lies= change of 76 address (confor to new su!net), or = s/ecial routing ta!le entries to forward /ackets to new su!net

Changing of 76 address – DN' u/dates take to long ti e – TC6 connections !reak – securit" /ro!le sChanging entries in routing ta!les – does not scale with the nu !er of o!ile hosts and fre%uent

changes in the location – securit" /ro!le s'olution re%uire ents – retain sa e 76 address, use sa e la"er /rotocols – authentication of registration essages,

Mo!ile 764 $asic 7dea


189/298


Ro+ter %

Ro+ter &

Ro+ter !

6 M3

8omea ent

Mo!ile 764 $asic 7dea


190/298


Ro+ter %

Ro+ter &

Ro+ter !

6 M3

8ome a ent

7orei n a ent

move

9ackets are t+nneled+sin I9 in I9


191/298

Data transfer to the o!ile s"ste8,

!


192/298


7nternet

sender

7,

M3

1ome network

*orei nnetwork

recei&er

%

!

&

.- 'ender sends to the 76 address of MN,

;A interce/ts /acket (/ro:" A#6)- ;A tunnels /acket to COA, here FA,

!" enca/sulation


193/298


7nternet

recei&er

7,

M3

1ome network

*orei nnetwork

sender

%

.- 'ender sends to the 76 address of the recei&er as usual, FA works as default router

'ource4 'chiller

/3

Mo!ile 764 $asic O/eration

Agent Ad&ertise ent


194/298


– ;A3FA /eriodicall" send ad&ertise ent essages into their/h"sical su!nets

– MN listens to these essages and detects, if it is in ho e3foreignnetwork

– MN reads a COA fro the FA ad&ertise ent essagesMN #egistration – MN signals COA to the ;A &ia the FA – ;A acknowledges &ia FA to MN – li ited lifeti e, need to !e secured !" authentication;A 6ro:" – ;A ad&ertises the 76 address of the MN (as for fi:ed s"ste s) – /ackets to the MN are sent to the ;A – inde/endent of changes in COA3FA6acket Tunneling – ;A to MN &ia FA

Mo!ile 764 Other 7ssues

#e&erse Tunneling


195/298


– firewalls /er it onl" Kto/ological correctK addresses – a /acket fro the MN enca/sulated !" the FA is nowto/ological correct

O/ti iEations – Triangular #outing

= ;A infor s sender the current location of MN

– Change of FA= new FA infor s old FA to a&oid /acket loss, old FA now

forwards re aining /ackets to new FA


196/298


Mesh and Adhoc Networks

Multi8;o/ Wireless


197/298


Ma" need to tra&erse ulti/le links to reach destination

Mo!ilit" causes route changes

Mo!ile Ad ;oc Networks (MAN9T)

;ost o&e ent fre%uent


198/298


;ost o&e ent fre%uent

To/olog" change fre%uent

No cellular infrastructure- Multi8ho/ wireless links-Data ust !e routed &ia inter ediate nodes-

BB

MAC in Ad hoc networks

l


199/298


7999 *+ -.. DCF is ost /o/ular – 9as" a&aila!ilit"*+ -.. DCF4 – Hses #T'8CT' to a&oid hidden ter inal /ro!le

– Hses AC> to achie&e relia!ilit"

*+ -.. was designed for single8ho/ wireless – Does not do well for ulti8ho/ ad hoc scenarios – #educed through/ut – 9:/osed ter inal /ro!le

9:/osed Ter inal 6ro!le


200/298


– A starts sending to $- – C senses carrier, finds ediu in use and has to

wait for A8R$ to end- – D is outside the range of A, therefore waiting is not

necessar"- – A and C are Ke:/osed ter inals

, ./

D

Distance8&ector Link8state #outing

$oth assu e router knows


201/298


$oth assu e router knows – address of each neigh!or – cost of reaching each neigh!or

$oth allow a router to deter ine glo!al routinginfor ation !" talking to its neigh!ors

Distance &ector 8 router knows cost to each destination

Link state 8 router knows entire network to/olog" andco /utes shortest /ath

Distance 0ector #outing4 9:a /le


202/298


2

Link 'tate #outing4 9:a /le


203/298


MAN9T #outing 6rotocols

6roacti&e /rotocols


204/298


– Traditional distri!uted shortest8/ath /rotocols – Maintain routes !etween e&er" host /air at all ti es – $ased on /eriodic u/dates ;igh routing o&erhead – 9:a /le4 D'D0 (destination se%uenced distance &ector)

#eacti&e /rotocols – Deter ine route if and when needed – 'ource initiates route disco&er" – 9:a /le4 D'# (d"na ic source routing)

;"!rid /rotocols – Ada/ti&e Co !ination of /roacti&e and reacti&e – 9:a /le 4 I#6 (Eone routing /rotocol)

D"na ic 'ource #outing (D'#)

#oute Disco&er" 6hase4


205/298


– 7nitiated !" source node ' that wants to send /acket todestination node D – #oute #e%uest (##91) floods through the network – 9ach node appends own identi ier when forwarding ##91#oute #e/l" 6hase4 – D on recei&ing the first ##91, sends a #oute #e/l" (##96) – ##96 is sent on a route o!tained !" re&ersing the route

a//ended to recei&ed ##91 – ##96 includes the route fro ' to D on which ##91 was

recei&ed !" node D

Data Forwarding 6hase4 – ' sends data to D !" source routing through inter ediate nodes

#oute disco&er" in D'#


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.

,

6 07

8

E

D

/

G

IJ

L

Represents a node t1at 1as received RR0@ *or D *rom 6

M

3

2


.roadcast transmission


207/298


.

,

6 07

8

E

D

/

G

IJ

Represents transmission o* RR0@

L

M

3

2

6N

X N Represents list o* identi*iers appended to RR0@



208/298


.

,

6 07

8

E

D

/

G

IJ

= 3ode 8 receives packet RR0@ *rom two nei 1


209/298


.

,

6 07

8

E

D

/

G

IJ

L

= 3ode D does not *orward RR0@


210/298


.

,

6 07

8

E

D

/

G

IJ

L

M

3

2

RR09 6 0 7 E DN

Represents RR09 control messa e

Data deli&er" in D'#


211/298


.

,

6 07

8

E

D

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